1. Field of the Invention
The invention relates to a lubricant dispenser comprising a housing, a lubricant supply container with a plunger connected with the housing, and an electromechanical drive.
2. The Prior Art
In an embodiment known from EP-A 0 845 631, the electromechanical drive comprises a spindle which is driven by a gear drive motor. The lubricant supply container has an outlet opening for lubricant, which is squeezed out by a movement of the plunger. The build-up of pressure in the lubricant supply container is limited. If large resistance to flow builds up on the outlet opening or in a line adjoining the opening; an overload protection device responds, which switches off the electromechanical drive; and the supply of the various lubrication points when lubricant is not assured. Furthermore, with dispensers known in the art, the lubricant supply container has to be exchanged. Line systems arranged downstream have to be detached from the lubricant supply container. If the electromechanical drive has an external power source and/or the lubricant dispenser is connected to a central control, electrical plug connections have to be pulled from the housing before the housing containing the electromechanical drive can be unscrewed from the lubricant supply container.
Furthermore, lubricant dispensers are known in the art, which comprise a lubricant supply container that is connected with the housing in a detachable manner. On the suction side of the plunger pump, a channel fixed on the housing adjoins the housing and feeds into the lubricant supply container. The housing accommodates the plunger pump, a control device, and possibly batteries for supplying the plunger pump with current. The housing also has an outlet channel that is connected with the pressure side of the plunger pump. The lubricant supply container contains a spring-loaded plunger which puts the lubricant supply under pressure and feeds the lubricant. This lubricant is highly viscous in most cases, such as grease, and feeds into the plunger pump on the suction side. Constantly admitting pressure to the lubricant supply poses the risk that the lubricant dispenser bleeds out, wherein small amounts of lubricant are constantly pressed out by the piston when pressure is applied. Furthermore, the plunger pump represents an aggregate that is relatively expensive.
The invention relates to an electromechanically operated lubricant dispenser that is simple in design and permits exactly metered dispensing of lubricant at high squeeze-out pressure. The supply of lubricant is not acted upon by a pressure spring-loaded plunger to avoid the risk of bleed-out.
The object of the invention is to provide a lubricant dispenser comprising a housing, a lubricant supply container with a plunger connected with the housing, a telescopic hollow spindle, and an electromechanical servo-drive for changing the length of the telescopic hollow spindle.
The telescopic hollow spindle is fixed on one end, of the housing. This hollow spindle has a lubricant passage channel, and cooperates on the other side with a plunger containing a passage opening for lubricant.
There is also at least one check valve that is arranged in the lubricant passage channel on the inlet side.
The telescopic hollow spindle alternately carries out setting strokes of different lengths that increase or shorten the length of the telescopic spindle.
The setting strokes are coordinated with each other wherein the telescopic hollow spindle moves through a setting stroke which increases the length of the spindle. A plunger moves to displace a preset amount of lubricant so that it enters the lubricant passage channel through the opening check valve. With a subsequent setting stroke reducing the length of the spindle, the preset amount of lubricant is squeezed out of the lubricant passage channel by the action of the closed check valve on the inlet side. In a preferred embodiment of the invention, the plunger is supported in the lubricant supply container with friction and torsional strength, by means of elastomer seals arranged on the periphery, and does not carry out any resetting movements.
With a setting stroke increasing the length of the spindle, the telescopic hollow spindle is driven against the plunger and presses the plunger forwards by a preset measure xcex94x. Thus, the lubricant is displaced and enters the lubricant passage channel of the telescopic hollow spindle through the opening check valve. With the subsequent setting stroke shortening the length of the spindle, the amount of lubricant previously supplied to the lubricant passage channel is squeezed out of the lubricant passage channel by contraction of the telescopic hollow spindle. The setting stroke of the telescopic hollow spindle increasing its length is by the measure xcex94x greater than the subsequent setting stroke reducing the length. The setting strokes are coupled kinematically, so that they can be precisely coordinated.
In a preferred embodiment of the invention, the telescopic hollow spindle comprises a tube arranged in a fixed manner on the housing, and a hollow spindle with an outer thread that is movably arranged on the tube and capable of sliding on the tube. A driving gear with an inside thread is arranged on the hollow spindle and rotatably supported in the housing with axial strength and driven by a pinion of the servo-drive. Gaskets, for example in the form of elastomer sealing rings are arranged between the tube and the hollow spindle. Furthermore, a second check valve should be arranged at the end of the lubricant passage channel on the outlet side.
Various possibilities are available for the constructional design of the servo-drive. According to a preferred embodiment, the servo-drive comprises a motor that is operated by a control in an alternating manner wherein it is capable of turning both in the right and left directions of rotation. Moreover, a geared motor can be used that comprises a reversing device for reversing the direction of rotation of the driving shaft. Furthermore, it is possible to associate two motors with the hollow spindle that have different directions of rotation and are controlled in an alternating manner.
As another development of the invention, the servo-drive has an electronic control with a sensor for picking up the measured value, which counts the number of the revolutions of the motor or of a pinion driven directly or indirectly by the motor. The electronic control then stops the electric motor after a preset number of revolutions. In addition, different values that are coordinated with the setting strokes of the telescopic hollow spindle are preset for the setting stroke increasing or reducing the length of the telescopic hollow spindle.
The plunger may comprise a pin having a passage opening. The end of the telescopic hollow spindle located on the plunger side is pushed onto the pin, whereby there is a seal arranged between the pin and the telescopic hollow spindle. In a preferred embodiment of the invention, the telescopic hollow spindle has a collar surface which impacts the plunger with a setting stroke increasing its length. Furthermore, the telescopic hollow spindle has an extension which is axially movably extended through the passage opening of the plunger and projects into the space of the lubricant supply container filled with lubricant. The plunger has a short outlet tube containing the passage opening, whereby there is a seal between the short outlet tube and the telescopic hollow spindle.
The lubricant supply container can be connected in a detachable manner with the housing. The housing can contain the servo-drive, the electronic control associated with the servo-drive, and the part of the telescopic hollow spindle that is fixed on the housing. The connection end of the telescopic hollow spindle that is movable in the longitudinal direction projects beyond one face side of the housing. The plunger is supported on the lubricant supply container with friction and with torsional strength. This plunger does not perform any resetting movements. When the plunger impacts the face of the lubricant supply container, the servo-drive is supplied with a return pulse by the associated electronic control. Next, the telescopic hollow spindle is driven back into a starting position. Because a short lubricant outlet tube is not arranged on the lubricant supply container and there are no lines for data transmission or power supply connected to the lubricant supply container, it is very simple and easy to replace the lubricant supply container.